Process of making holes in a plate to be used in a heat exchanger

ABSTRACT

This invention is concerned with a process of making holes with a surrounding collar by a combined punching and drawing operation, hereinafter called &#39;&#39;&#39;&#39;draw-punching,&#39;&#39;&#39;&#39; in the so called end plates of a heat exchanger for inserting the tubes of heat exchangers of the type comprising distributing and collecting vessels i.e. headers for a heat exchanging medium and rows of tubes of flattened cross section with their flat sides turned towards each other arranged between said vessels. According to the invention, before draw-punching the holes, an elongated, preferably rectangular recess is pressed for each row of tubes, the recess having a length at least equal to the length of the tube row, a width less than the length of the tube cross section and a depth approximately equal to the height of the collar formed around the edge of each hole, the recess having along its longitudinal sides at the locations of junction of the tubes opposite with the end plate pairwise opposed widened portions corresponding in shape and size to the end portions of the tube cross sections extending outside the longitudinal sides of the recess.

United States Patent 72] Inventor Rolv Gunnar Josok Oloistrom, Sweden [21 1 Appl. No. 880,568 [22] Filed Nov. 28, 1969 [45] Patented Dec. 7, 1971 [73] Assignee Oloistrom AB Ololstrom, Sweden [32] Priority Dec. 3, 1968 [33] Sweden [31 16479/68 [54] PROCESS OF MAKING HOLES IN A PLATE TO BE USED IN A HEAT EXCHANGER 1 Claim, 5 Drawing Figs.

[52] U.S.Cl ll3/1l8C, 72/334 [51] lnt.Cl B2ld 53/04 [50] Field of Search 113/1 C, 118C, 118 R; 72/334, 347; 165/151; 29/157.3 C

[56] References Cited UNITED STATES PATENTS 2,091,593 8/1937 Herz 165/151 3,182,483 5/1965 Karamazin 72/350 3,211,118 10/1965 Donaldson 1l3/ll8R FORElGN PATENTS 621,332 6/1961 Canada 113/118 R Primary Examiner-Richard .l. Herbst Attorney-Pierce, Scheffler & Parker ABSTRACT: This invention is concerned with a process of 5 exchanging medium and rows of tubes of flattened cross section with their flat sides turned towards each other arranged between said vessels. According to the invention, before drawpunching the holes, an elongated, preferably rectangular recess is pressed for each row of tubes, the recess having a length at least equal to the length of the tube row, a width less than the length of the tube cross section and a depth approximately equal to the height of the collar formed around the edge of each hole, the recess having along its longitudinal sides at the locations of junction of the tubes opposite with the end plate pairwise opposed widened portions corresponding in shape and size to the end portions of the tube cross sections extending outside the longitudinal sides of the recess.

PROCESS OF MAKING HOLES IN A PLATE TO BE USED IN A HEAT EXCHANGER The most usual example of heat exchangers of the kind considered are motor car coolers. The following description will therefore refer to motor car coolers though the invention is not limited to these. A motor car cooler has two spaced distributing and collecting vessels i.e. headers for liquid heat exchanging medium, generally water. These headers are interconnected by one or several rows of tubes of elongated cross section with thin tins in heat transmitting connection with the tubes.

The tubes are connected to plates, here called end plates forming the bottom and the top wall of the distribution and collecting headers respectively, or their sidewalls, depending on whether the tubes are vertical or horizontal. The tubes are inserted through correspondingly elongated holes provided in the plates. As indicated, the sealing is obtained by soldering. The tubes have a flattened i.e. elongated cross section and the holes have correspondingly a length of about 20 mm. and a width of about 2 mm. These holes are formed by drawpunching, which is a simple operation and which automatically provides upstanding edge collars, which are of importance for the tightness and the resistance of the soldered joint. The soldering between the end plates and the tubes can be effected in different manners, e.g., by dipping in a tin bath or melting a tin foil wound around each tube at the inside of the end plate.

It is evident that the collar around each hole in the end plates must have a certain height to permit a sufficient amount of tin to creep by capillary action into the space between the collar and the tube inserted therein. Experience has, however, shown that the collar normally does not receive the required height of about 1 to 2 mm. around the hole. This depends on" the fact that the necessary drawing of the plate at the ends of the elongated holes cannot beeffected without ruptures. By combined punching and drawing it is mostly not possible to obtain a greater height of the collar than about 0.8 times the thickness of the plate when the collar is to be formed by drawing of the material. Since the thickness of the end plates generally is about 0.5 mm., the height of the collar will evidently be too low at the ends of the elongated holes to permit the formation of a satisfactory soldering joint at this place. If the soldered joint does not become infallibly tight by soldering, which is generally effected in an automatic device, this causes important economical losses since time robbing and costly corrections of the product often have to be made. Such corrections must of course be avoided as far as possible in an automatic manufacturing process.

Efforts have been made to eliminate the above mentioned insecurity in the production by pressing a recess in the end plate in the places where the holes were to be punched previously to punching the hole. The intention was to produce a collar of sufiicient height before the hole itself was made by draw-punching. Such a process is, however, onerous because the pressing due to the unfavorable dimensions has to be performed in at least two steps with intermediate heating to obtain a sufficient depth of the pressed recess and thereby a sufficient height of the resulting collar. The problem to be solved was to make it possible to make holes in the end plates by combined punching and drawing in such manner that a collar of uninterrupted and sufficient height could be obtained thereby without the necessity to perform an onerous pressing operation in several steps. This problem is solved by the present invention.

In the following description an embodiment of the invention is described as an example with reference to the accompanying drawing.

FIG. 1 shows a vertical section through the upper portion of a motor car cooler with vertical tubes seen from the front side.

FIG. 2 shows a portion of an end plate seen from above when positioned as in FIG. 1 but before punching the holes for the tubes.

FIG. 3 shows a cross section taken along line Ill-III in FIG. 2.

FIG. 4 shows the end plate according to FIG. 2 after the punching of the holes.

FIG. 5 shows a cross section taken along line V-V in FIG. 4.

As shown in FIG. 1 the cooler has a distribution header 1 with an inlet 2, a row of tubes 3 with fins 4 and an upper end plate 5, which in this case forms the bottom wall of the distribution header 1. The tubes have a flattened cross section and are turned with their flat sides towards each other. They are inserted through holes 6 in the end plate. The holes have collars 7 along their edges. The tubes are united to the end plate by soldering.

Before the holes for a row of tubes are made into the end plate by draw-punching, an elongated recess 8 is pressed therein as shown in FIGS. 2 and 3. In the embodiment illustrated the cooler has two rows of tubes and the end plate is therefore provided with two of such pressed-in recesses 8. Each recess is rectangular and at least as long as the appertaining row of tubes. In the drawing the recess is shown to be a little longer than the tube row. The recess is further placed symmetrically with the tube row. The width of the recesses 8 is less than the length of the cross section of the tubes, but along both sides the recess has widened portions 9 placed in pairs opposite each other in the places where the tubes are to be inserted and where the holes thus are to be punched. These widened portions correspond in shape and dimension to the portions of the length of the tube section which project past the width of the recess. It has been found advantageous to give the recess a width of about 60 to percent of the length of the tube section. Its depth and even that of the widened portions, is about equal to the desired height of the collar, which is to be formed around the holes finally punched.

The pressing operation described above can be effected to the necessary depth in one single pressing operation without fissures appearing at the widened portions 9. By this pressing operation the end portions 10 of the collars are thus formed to the desired height without ruptures.

After having prepressed the end plates in the manner above described, the holes for the tubes are made by draw-punching in the ordinary manner. FIG. 4 shows the end plate after the punching of the holes. Thereby a collar 7 is formed around the hole, which has the desired and continuous height even at the ends of the holes. When soldering the joint between the end plates and the tubes after these have been inserted into the holes, a sufficiently high and narrow gap is obtained around the entire tube to draw the tin by capillary action from adjacent parts so as to obtain an unfailingly tight joint. It has been found in practice that on automatic performance of the soldering all rejections and onerous repairs of the joint after the soldering operation are nearly completely eliminated.

Besides the advantages above indicated of the process according to the invention a further valuable advantage is obtained. Because of the elongated, rectangular recesses pressed into the end plates an important stiffening of these plates is obtained. It is therefore possible, when using the process according to the invention, to make the end plates of thinner material than before. This in its turn, of course, results in that the cooler even for this reason can be manufactured at a lower price and with less weight than it was possible before.

As mentioned the invention is not limited to motor car coolers but can also be used in connection with any other heat exchanger of similar type.

I claim:

1. The process for making that wall plate of a header for a heat exchanger having at least one row of parallel spaced elongated holes therein and through which the end portions of a row of parallel spaced liquid coolant carrying tubes of correspondingly elongated cross section are passed and soldered to collars around the edges of the holes which comprises the steps of:

pressing an elongated recess into the plate for each row of tubes, said recess having a length at least equal to the length of the tube row, a width less than the length of the elongated tube section and a depth approximately equal to the desired height of the hole collar, said elongated recess also including along the opposite longitudinal sides, and at those places where the tubes are to be located, widened portions located opposite each other in pairs and corresponding in shape and dimensions to those portions of the ends of the tube sections projecting out- 5 side the longitudinal sides of said pressed-in recess, and draw-punching the holes along the recess at the paired widened portions.

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1. The process for making that wall plate of a header for a heat exchanger having at least one row of parallel spaced elongated holes therein and through which the end portions of a row of parallel spaced liquid coolant carrying tubes of correspondingly elongated cross section are passed and soldered to collars around the edges of the holes which comprises the steps of: pressing an elongated recess into the plate for each row of tubes, said recess having a length at least equal to the length of the tube row, a width less than the length of the elongated tube section and a depth approximately equal to the desired height of the hole collar, said elongated recess also including along the opposite longitudinal sides, and at those places where the tubes are to be located, widened portions located opposite each other in pairs and corresponding in shape and dimensions to those portions of the ends of the tube sections projecting outside the longitudinal sides of said pressed-in recess, and draw-punching the holes along the recess at the paired widened portions. 